1. Field of the Invention
The present invention relates to a display device in which self-light emission type elements such as organic electroluminescence (EL) elements are disposed, and more particularly to a display device in which elements, for emitting lights having respective colors, each having a cavity structure are provided.
2. Description of Related Art
In recent years, an organic electroluminescence (EL) display device using organic EL elements has been put into practical use as a display device substituted for a liquid crystal display device. The organic EL display device has a wider view angle than that in the liquid crystal display device because it is of a self-light emission type. In addition, the organic EL display device is expected to have a sufficient response to a high-speed video signal for high definition.
Up to this day, for the organic EL element, by introducing a cavity structure, color purities of emission colors have been enhanced, and luminance efficiency has been improved, and so forth. In such a way, there has been made the attempt to control the lights emitted from light emitting layers, respectively. However, when the resonator structure is introduced into the organic EL element, light extraction efficiency in a front direction is enhanced for a displayed picture because a spectrum of a resonated light is high in peak and narrow in width. On the other hand, in this case, there is a problem that when the picture is viewed from an oblique direction, an emission wavelength is largely shifted, and emission intensity is reduced.
In order to cope with the above problem, a structure is proposed such that an optical distance of a resonation portion is set as a minimum value so as to fall within the condition range meeting the cavity structure, which results in that by holding a peak width while a peak intensity of a spectrum of an extracted light is increased based on a cavity effect, even when a view angle is shifted, a shift amount of wavelength is reduced, and a color purity is enhanced so as to fall within a wide view angle. This structure, for example, is described in PCT Patent Publication No. WO01/39554 (pamphlet) (hereinafter referred to as Patent Document 1) and Japanese Patent Laid-Open No. 2006-147598 (hereinafter referred to as Patent Document 2).
In addition thereto, an attempt is made such that a light emitting portion of an organic EL element having a resonator structure is formed in the form of a concave structure, and a light diffusing portion and a light deflecting portion are provided on a transparent substrate on a light-extracting side of the organic EL element, which results in that an emission direction of a light is diffused to average a directionality of the light, thereby increasing a view angle. This attempt, for example, is disclosed in Japanese Patent Laid-Open No. Hei 9-190883 (hereinafter referred to as Patent Document 3).